The present invention generally relates to the field of semiconductor manufacture, and more particularly to accurately seating semiconductor packages for electronic testing.
Quality control in the manufacturing of semiconductor packages is an increasingly important and costly aspect of the assembly process. Semiconductor package quality is controlled during the assembly process through intermediate and final product testing that assesses the physical and functional integrity of semiconductor packages.
Semiconductor package manufacturers implement intermediate testing procedures because they allow manufacturers to identify assembly errors before a final product has been made, thereby making any necessary semiconductor package rework less costly for several reasons. Intermediate testing allows manufacturers to more easily isolate where a semiconductor package assembly error occurred and the cause of the malfunction in a particular semiconductor package. For example, if a semiconductor package has only gone through solder and reflow steps, a manufacturer can determine that these assembly steps are the source of the semiconductor package malfunction before expending resources looking for problems more commonly associated with other assembly steps that have not yet occurred or that would have already been identified through prior testing procedures. Intermediate testing also reduces manufacturing costs because fewer parts are disassembled, examined and reassembled in order to identify an assembly error and repair the semiconductor package accordingly.
While intermediate testing affords manufacturers early assembly error detection, semiconductor package manufacturers also test the final semiconductor package to ensure that the fully assembled semiconductor package functions as intended. Under ideal circumstances, end-to-end testing ensures that semiconductor package manufacturers enjoy high production yields at the lowest possible cost. However, just as assembly errors leading to semiconductor package malfunction occur during or as a result of any of the assembly steps between testing procedures, testing itself can damage a semiconductor package.
In accordance with conventional testing methods, a semiconductor package is seated in a test socket comprising contacts that align with electrical leads on the semiconductor package. A plunger controlled by a test socket control system, is then lowered to engage the test socket and semiconductor package so that the test socket can electrically communicate with the semiconductor package through the aligned contacts and electrical leads. Once testing is complete, the plunger is lifted from the semiconductor package and the semiconductor package is removed.
Testing a semiconductor package positioned in a test socket is implemented by delivering test instructions from the test socket control system to the semiconductor package and recording the results. The test data is then analyzed and the integrity of semiconductor package is assessed. Semiconductor package manufacturers identify the circumstances under which a semiconductor package ceases to properly operate under test conditions by monitoring the variants at which the computational tests fail. A semiconductor package that correctly responds to a plurality of different test instructions by generating known predetermined outputs is assessed as having good integrity.
There are several disadvantages to conventional methods of testing semiconductor packages. One disadvantage is the damage caused by the plunger when lowered onto a test socket where the semiconductor package is not properly seated. For example, it is important to ensure that the semiconductor package is facing the correct direction, e.g., face up or face down, and is oriented properly, e.g., as when components are located in a particular position relative to the semiconductor package, to complete testing. If the semiconductor package is not properly seated, the pressure from the plunger lowered onto the semiconductor package will damage the test socket and the semiconductor package. Similarly, when the plunger is lowered onto a semiconductor package that is improperly orientated on the test socket, the electrical leads of the semiconductor package are not aligned with corresponding contacts of the test socket. If the improper orientation of a semiconductor package is not realized before the plunger is lowered onto the test socket, the improperly orientated semiconductor package and the test socket will be damaged. This practice is a waste of semiconductor package manufacturer resources because of lost time associated with semiconductor package rework, lost revenue stemming from reduced production yield, and costly and time consuming test socket repair or replacement.
In addition to the physical damage that occurs when a package is not properly seated in the test socket, improper placement also triggers false test results. For example, if a semiconductor package leads do not fully connect with the test socket contacts, the test can suggest a bad semiconductor package when the real cause of the problem is improper semiconductor package seating. This error type necessitates unnecessary additional testing and/or semiconductor package rework. Conventional testing methods make it difficult to avoid these problems because they lack the ability to easily and repeatedly monitor semiconductor package seating on a test socket before and during testing to avoid initiating or continuing testing when a semiconductor package is not properly seated in a test socket.
There exists a need for the ability to monitor and identify semiconductor packages in a testing apparatus in preparation for and during testing procedures.
The present invention provides an apparatus for testing semiconductor packages, the apparatus having a test plunger, a test socket configured to seat a semiconductor package, a vacuum sensor with a sensing element for detecting semiconductor package seating and a monitoring mechanism. The sensing element is attached in a through-hole that passes through the center ground plane of the test socket. The vacuum sensor includes a suction generator arranged so that air suctioned through the through-hole creates a high vacuum level when a semiconductor package is properly seated in the test socket and a low vacuum level when a semiconductor package is improperly seated in the test socket. The monitoring mechanism, which is attached to the vacuum sensor, determines whether a semiconductor package is properly seated in the test socket based on the vacuum level created by the suctioned air. A signal is generated when the vacuum level is low, thereby preventing the test plunger from lowering onto the improperly seated semiconductor package to initiate testing.
An advantage of the present invention is the prevention of test initiation when a package is not properly seated in the test socket, thereby reducing or eliminating damage to the semiconductor package and test socket caused by conventional testing methods when the test plunger is lowered onto the improperly seated semiconductor package.
The present invention also advantageously improves semiconductor package production efficiencies by reducing the costs associated with semiconductor package damage, unnecessary semiconductor package rework, equipment repair and replacement, and repetitive testing.
Another aspect of the present invention provides a method for testing semiconductor packages. The method includes the steps of placing a semiconductor package in a test socket of a testing apparatus and determining whether the semiconductor package is properly seated in the test socket in preparation for testing. Air is suctioned through a through-hole that passes through the center ground plane of the test socket to create a vacuum, which is used to detect whether a semiconductor package is properly seated in the test socket. A determination is made about the semiconductor package seating, whereby a semiconductor package is determined to be improperly seated in the test socket when air suctioned through the through-hole creates a low vacuum level and properly seated when the air suctioned through the through-hole creates a high vacuum level. A signal is generated when the monitoring mechanism determines that a semiconductor package is improperly seated and the test plunger is inactivated, thereby stopping test initiation. In response to a determination that a semiconductor package is properly seated in the test socket, a signal is generated, thereby activating the test plunger and initiating testing.
The present invention advantageously improves production output due to fewer damaged semiconductor packages and test sockets. The manufacturing process is also simplified by reducing or eliminating the amount of semiconductor rework and testing oversight that a semiconductor manufacturer must conduct.
Other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description. The embodiment shown and described provides illustration of the best mode contemplated for carrying out the invention. The invention is capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawing is to be regarded as illustrative in nature, and not as restrictive.